The present invention generally relates to a strain gauge joystick supplying signals representative of a manipulation force liable to be exerted in any radial direction with respect to the joystick and further including an enabling button.
In various applications, for example in some interactive electronic games, a control joystick, designed to be operated with one hand and liable to be moved in any radial direction, is provided. In some applications, it is further useful to associate to such a joystick a push-button that can be activated at any time, with the same hand, for example for enabling a specific manipulation.
Such a joystick is generally constituted by a supporting part in which is embedded a solid flexible stick comprising at its free end a control lever and bearing four strain gauges circumferentially arranged at regularly spaced points. The four strain gauges are usually bridge-connected and supply electric signals representative of the displacement of the hand lever in a plane perpendicular to the longitudinal axis of the hand lever.
The flexible stick is generally relatively stiff, so that its flection remains low when manipulated at the maximum allowed strength. Generally, one uses a steel stick having a few millimeters in diameter and a few centimeters in length, thus forming a joystick having the shape of a small-diameter and small-length lever that can be held within one hand.
It is known to associate to such joystick a unit constituted by an enabling push-button and a switch activated by this push-button. The push-button is then arranged at the end of the stick and the switch is positioned at the side of the stick. Therefore, the joystick does not have a symmetrical shape with respect to the longitudinal axis of the flexible stick, because of the lateral position of the switch. Such an arrangement causes manufacturing problems due to the fact the push-button eccentrically activates the switch and causes assembly difficulties because the laterally arranged switch increases the overall size of the unit.
It is generally provided to accommodate the unit formed by the flexible stick and the switch in a fixed cylindric envelope, the flexible stick and the cylindric envelope being coaxially arranged. With this cylindric envelope, the external shape of the joystick is cylindrical, ensuring a physical protection of the switch. The inner diameter of the cylindric envelope has a minimum size equal to twice the size of the switch in the radial direction, not including the diameter of the flexible stick. This arrangement involves that either the cylindric envelope has a relatively large diameter which impairs its mounting, or the switch, and the possible intermediate parts transmitting the motion of the push-button to the switch, must be highly miniaturized, which causes extra costs or a decreased reliability of the joystick.
For example, the joystick can be associated to a plane control handle. The handle has to be highly reliable and have a small size, despite the numerous control devices provided thereon.
An object of the invention is to provide a strain gauge joystick equipped with an enabling push-button, in the form of a small-size cylindric lever with a reduced diameter and length.
Another object of the invention is to provide a joystick with minimum complexity and higher reliability.